This project is aimed at enhancing our knowledge and understanding of the genetic bases of reading and related processes. It has long been known that reading, whether qualified as ability or disabilities, along with reading-related processes, are heritable, but it has been rather difficult for the field to converge on specific gene candidates for this (dis)ability. The field has identified a number of reasons for such a lack of convergence among the molecular-genetic findings. These reasons include lack of power, inconsistencies in phenotypic evaluations, and, perhaps, the focus on English, which is a particular outlier among world languages. In this application, we attempt to overcome some of the limitations of previous studies by working with large samples of Russian-speaking siblings (n = 400 pairs) and discrepant singletons (n = 1,500), whose performance on reading and reading-related assessments is carefully sampled through an assessment battery embedded in a particular theoretical framework. We will capitalize on preliminary findings obtained through a whole-genome short-tandem-repeat-polymorphism (STRP) linkage study (WGLS) of Russian sib pairs and propose to complete a single-nucleotide-polymorphism (SNP)-based investigation of the regions of interest identified in the WGLS using ~4,500 targeted SNPs genotyped on the DNA from these 2300 individuals (sib pairs and singletons) and multivariate reading-related phenotypes. The proposed combination of samples, skills, and technologies provides a rather appealing opportunity, both scientifically and methodologically. This R21 will generate pilot data to (1) establish the feasibility of constructing a large epidemiologically-based sample of Russian children with specific reading disability (SRD);(2) investigate the usability of combining STRP and SNP data obtained on the same sample;and (3) estimate the sizes of genetic effects, if confirmed, and design subsequent studies utilizing more definitive and funding-demanding technologies (e.g., sequencing). PUBLIC HEALTH RELEVANCE: Difficulties in reading acquisition and performance are common and observed at the prevalence of 5-7% in all studied countries, regardless of the characteristics of the writing system within a given country. Years of research into the manifestation and etiology of these difficulties have established that it is a life-long condition unfolding at high cost to an individual, associated with lost years of education, diminished career success, and often negative mental health outcomes. Understanding the etiology of reading difficulties is crucial for developing adequate methods for its prevention and remediation.